Device and method for locking a rim of a wheel to a turntable

ABSTRACT

Described is a device for locking a rim of a wheel to a wheel-holder unit (4) equipped with a supporting plate (12) and a hollow rotary shaft having an end portion projecting in a cantilever fashion from the supporting plate (12), comprising: a centring cone (16) having a through hole; a clamping rod (11) having at a first end a clamping element (10) which can be inserted inside the hollow shaft to prevent a movement of the clamping rod (11) along a first axis (A) of the wheel-holder unit (4), and having at a second end a threaded portion; a clamping element (17) coupled to the threaded portion and which can be rotated for translating along an axis of the clamping rod; a centring flange (23) operatively interposed between the centring cone (16) and the clamping element (17). The first end of the clamping rod (11) is operatively inserted in a hole of the centring flange (23), with the same direction as that in which centring rods (23b) of the centring flange project, and in the hole of the centring cone (16), with the opposite direction to that along which the centring cone (16) is tapered.

TECHNICAL FIELD

This invention relates to a device for locking a rim of a wheel to awheel-holder unit.

BACKGROUND ART

The invention applies to the field of equipment for tyre repairspecialists and in particular to that of the wheel service machines.

It should be noted that the term wheel (for vehicle) means the couplingbetween a tyre and a corresponding rim (that is, the overall tyre/rim).

Wheel service machines are divided into two main types:

-   -   balancing machines, configured to measure the static and/or        dynamic unbalancing of a wheel;    -   machines for fitting and removing a tyre on a corresponding rim        (also known in the prior art as a “tyre changer machine”).

The balancing of a wheel for a vehicle is performed by the tyre repairspecialist in order to eliminate or reduce to a minimum the effects ofthe asymmetric distribution of the weights of the tyre/rim assembly.These asymmetries are usually compensated for by the tyre repairspecialist by fixing counterweights to the rim.

The asymmetry is caused by the non perfect roundness of the tyre or ofthe rim. This is due basically to machining defects, non-homogeneity ofconstruction materials, and the existence of inflation valves which,although relatively light in weight, constitute additional unbalancedweights. Further causes of the wheel unbalance are linked, for example,to deformation of the rims (caused by impacts and deep potholes), out ofroundness of the tyre after a certain mileage, flattening of the treadduring sharp braking, and errors during fitting and removal of thewheel.

These unbalances generate forces which cause annoying vibrations at thesteering wheel, chassis and frame of the vehicle, in particular at highspeeds.

The forces are called, depending on the direction in which act:

-   -   radial forces (in a direction which connects the centre of the        rim to the tyre tread);    -   lateral forces (in the direction of the axis of rotation of the        wheel);    -   tangential forces (in a direction which is tangential to the        tread).

The asymmetries and non-uniformity of the rim/tyre assembly causevariations to the radial, lateral and tangential force during rotationof the wheel subjected to a load.

Balancing machines comprise a frame from which a motorised spindleprotrudes. A locking system makes it possible to fix the rim to thespindle, in such a way that the wheel can be placed in rotation in orderto perform the measurements needed for the balancing operations. Thesemachines measure the wheel unbalance by analysing the timing andamplitude of the mechanical vibrations which are generated by rotatingthe wheel. The mechanical vibrations are measured in terms of movements,forces or pressures, by using transducers which convert the measurementscollected into electrical signals. Balancing machines indicate to theuser the weight and the position on the rim at which to fix thecounterweights.

Machines for fitting and removing a tyre on a rim comprise awheel-holder unit and at least one operating unit. The wheel-holder unitusually comprises a locking system which fixes the rim which fixed to arotary supporting plate, to set it in rotation about its axis ofrotation. The operating unit is usually equipped with numerous tools,used for bead breaking, removing and fitting the tyre.

During the removal, the wheel is fixed to the wheel-holder unit and setin rotation whilst a removal tool, located in the stationary positionrelative to the movement of the rim, is operated so as to grip a portionof a bead of the tyre and extract it from the seat of the rim. The seatof the rim is formed by the zone between the flanges (that is, annularedges) of the rim.

During the fitting, the rim is fixed to the wheel-holder unit and set inrotation whilst a fitting tool, located in the stationary positionrelative to the movement of the rim, is operated so as to force a zoneof a bead of the tyre inside the seat of the rim.

The two types of wheel service machines, that is, balancing and tyrechanger, have different features and requirements.

In the balancing machines, the wheel is rotated at an angular speedgreater than that of the tyre changer machines.

In order to measure the unbalances and the forces with a high degree ofaccuracy, the balancing machines require a system for locking the rimwhich is particularly precise and stable. More specifically, the systemfor locking the rim must be able to centre the rim extremely preciselyand maintain this precision during rotation of the wheel.

In the tyre changer machines, the speed of rotation of the rim is less,but the action of the tools of the operating unit on the tyre generateshigh forces, which have an effect on the wheel-holder unit and on theframe of the machine. For this reason, the wheel-holder unit and thelocking system of the tyre changer machines must be particularly robustand reliable.

There are also prior art wheel service machines equipped with a loadroller, which, positioned at the periphery of the tyre, simulates a loadapplied to the tread during rotation of the wheel.

Examples of balancing machines equipped with a load roller are describedin patent documents U.S. Pat. No. 8,250,915B1 and U.S. Pat. No.6,405,591B1. Examples of tyre changer machines equipped with a loadroller are described in patent documents U.S. Pat. No. 8,250,915B1,WO2014/129476A1, EP2468541A1, CN101298231A and EP2361791B1.

The use of the roller in a wheel service machine has the advantage ofproviding information useful to the tyre repair specialist, but thereare various issues. In fact, the tyre service specialist with usefulinformation. In effect, even if the vehicle wheel is balanced bycounterweights, some non-uniformity in the tyre structure may give riseto lateral forces when the wheel is set in rotation under the action ofa load

One issue concerns the fixing or locking of the wheel on the rotarywheel-holder unit, in particular in the case of tyre changer machines.The locking system used in the tyre changer machines is robust, but itis a relatively imprecise. This limits the accuracy of the measurementsperformed with the roller, thus adversely affecting the reliability.

Another issue concerns the overall dimensions, as the roller tends bebulky. That issue is particularly felt in the case of tyre changermachines equipped with a roller, as the tyre changer machines areequipped with numerous tools, which must be used by the tyre repairspecialist on the wheel, simultaneously with or at different stages ofthe use of the tyre changer machine (for example, bead breakers,removal, fitting). In light of this, it should be noted that it alsoimportant that the tyre repair specialist has a large free space formoving around the wheel.

Thus, a tyre changer machine has an operating unit comprising aplurality of tools, to which the roller is added. For this reason, it isnecessary to avoid interference between the tools of the operating unitand the roller itself. It is also necessary to allow the tyre repairspecialist to alternately use the load roller and the tools of theoperating unit in a reliable and fast manner, without losing time; it isalso necessary to provide the tyre repair specialist with operatingspace which is as large as possible.

To improve the characteristics of the tyre and reduce itsnon-uniformity, the tyre service specialist usually removes parts of thetyre from the tread. In actual fact, this solution constitutes only atemporary remedy which often proves unsatisfactory because the amplitudeof the vibrations produced remains high. Further, removing parts of thetyre from the tread means reducing the thickness of the tread and,consequently, shortening the working life of the tyre.

Among the causes of lateral forces connected with non-uniformity of tyrestructure are defects known as conicity and ply steer.

To better understand the concept of conicity, let us imagine that duringrotation, a wheel subjected to a load adopts a frusto-conical shape(that is, a first side wall of the tyre is larger in diameter than asecond side wall. Consequently, it generates a force directed towardsthe apex of the cone from the first side wall to the second side wall.It should be noted that this force does not change direction if thedirection of rotation of the wheel is reversed. By definition,

${Conicità} = \frac{{FLT}_{cw} + {FLT}_{ccw}}{2}$where FLT_(cw) denotes a total lateral force measured in a firstdirection of rotation and FLT_(ccw) denotes a total lateral forcemeasured in a second direction of rotation opposite to the first.

Conicity is generally associated with non-uniformity in the tyrestructure such that one side wall is more rigid than the other.

Ply steer generates lateral forces which can cause the vehicle todeviate from a straight direction of travel. These forces are generatedby non-uniformity in the distribution of the outer ply layers of thetyre. These forces change direction if the direction of rotation of thewheel is reversed. By definition,

${Plysteer} = \frac{{FLT}_{cw} - {FLT}_{ccw}}{2}$where FLT_(cw) denotes a total lateral force measured in a firstdirection of rotation and FLT_(ccw) denotes a total lateral forcemeasured in a second direction of rotation opposite to the first.

Further information useful for the tyre service specialist can beobtained by measuring the rolling radius. On account of tyre flattening,the rolling radius of the wheel (that is, the distance between the axisof rotation of the wheel and the point of contact between tyre and loadroller) is smaller than the nominal radius of the wheel (that is, theradius of the wheel when not subjected to a load). The industryreference standards (for example, ETRTO Standards Manual) define thetheoretical rolling circumference, that is, the value of the dynamiccircumference theoretically adopted by the wheel when subjected to amaximum predetermined load, at a speed of rotation of 60 km/h and areference inflation pressure, as follows.C _(din) _(_) _(lim)=3.05d _(n)where d_(n) is the nominal diameter of the wheel (that is, the diameterof the wheel not subjected to the action of a load). To verify thesestandards, it is therefore necessary to set the wheel in rotation at arelatively high speed which wheel service machines, especially tyrechanger machines, are not capable of reaching.

Another issue relates in general to all the wheel service machinesequipped with a roller, and it relates to the completeness and theactual utility for diagnostic purposes of the data provided to themachine thanks to the measurements of the roller.

The wheel service machines equipped with a load roller provide datarelating to a variation in the radial force (Radial Force Variation,RFV) and tangential force (Lateral Force Variation, LFV) during rotationof the wheel; moreover, a further parameter which may be measured by thewheel service machines equipped with a load roller is the conicity (byrotating the tyre in both directions), which depends on the behaviour ofthe lateral force.

However, these measurements do not allow defects to be distinguishedwhich are linked to the conicity, or, more generally, the elasticresponse of the wheel, from defects which are linked to the structure ofthe tyre (due, for example, by possible damage). Moreover, thesemeasurements do not provide diagnostic information on the noise level ofthe tyre.

DISCLOSURE OF THE INVENTION

The aim of this invention is to overcome the above-mentioned issues ofthe prior art.

Thus aim is fully achieved according to this invention as characterizedin the appended claims.

One aim of this disclosure is to provide a wheel service machine and arelative method of use which are particularly useful and easy to use bythe tyre repair specialist.

Another aim of this disclosure is to provide a wheel service machine anda relative method which are particularly useful and easy to use by thetyre repair specialist.

More specifically, an aim of this disclosure is to provide a tyrechanger machine and a relative method of use which provide diagnosticinformation on the wheel which is particularly complete and significant.

Another aim of this disclosure is to provide a locking device for fixingthe wheel to the wheel-holder unit, in a wheel service machine, which isparticularly robust and precise.

In an example embodiment according to this disclosure, a tyre changermachine is provided equipped with a roller, which leaves the tyre repairspecialist an ample space for operating around the wheel and whichallows the tyre repair specialist to alternate the use of differenttools, including the roller and the removal tool, in a particularly fastand effective manner.

This refers in particular to a machine for fitting and removing a tyrefrom a corresponding rim of a vehicle wheel.

In this embodiment, the tyre changer machine comprises a wheel-holderunit, which rotates about an axis; the wheel-holder unit is motordriven. Moreover, the tyre changer machine comprises at least one beadbreaker tool, which is movable along a second axis parallel to the firstaxis.

The tyre changer machine also comprises a roller, rotating about afourth axis parallel to the first axis. The roller can also rotate,together with a supporting structure of the roller, about a fifth axisspaced from the fourth axis, between an active position, where it is incontact with a tyre tread of the wheel mounted on the wheel-holder unit,to a non-interference position relative to the tyre. At least one sensor(preferably a sensor force) is connected to the roller to detect asignal representing a force transmitted to the roller by the tyre.

The tyre changer machine also comprises a removal tool (which is coupledto a fitting tool, or which also acts as a fitting tool).

According to an example, the wheel service machine according to thedisclosure comprises a frame and a wheel-holder unit which rotates abouta first axis of rotation. The machine comprises a roller which rotatesabout an axis parallel to the first axis. The roller is movable towardsand away from the wheel-holder unit along an operating trajectory suchthat the axis of the roller remains parallel to the first axis. Theroller is movable between a position of non-interference with the tyreof a wheel mounted on the wheel-holder unit and an active position whereit applies a predetermined force to the tyre tread. The machinecomprises a connecting structure to movably connect the roller to theframe.

The machine comprises at least one force sensor connected to the rollerfor measuring values of a force parameter representing a radial forcetransmitted to the roller by the tyre.

The machine comprises at least one position sensor configured to measurevalues of a position parameter representing a position of the rollerrelative to the frame.

The machine according to the disclosure comprises a processing unitconnected to the force sensor and to the position sensor to calculate,as a function of the position parameter, a geometrical parameterrepresenting a distance between the first axis and a surface of theroller in contact with the tyre tread when the roller is in the activeposition. The processing unit is programmed to derive a pair of valuescomprising a value of the radial force measured by the force sensor whenthe roller is in the active position and a corresponding value of thegeometrical parameter calculated.

It should be noted that this solution provides the tyre servicespecialist with information representing the rolling radius of theroller, thus giving the tyre service specialist information which ismore complete and useful for diagnostic purposes.

In one example embodiment, the wheel service machine is a tyre changermachine.

In an example embodiment, the position sensor is coupled to theconnecting structure at a predetermined position to detect apredetermined zone of the connecting structure where the processing unitholds in its memory information representing the relative positionbetween the predetermined zone and the axis of the roller. Preferably,the connecting structure comprises an articulated arm connected to theroller to move the roller by rotation about its own axis, which isspaced from the axis of the roller. Preferably, the position sensor isconfigured to derive a rotation of the articulated arm relative to theframe.

It should be noted that this solution allows tracing the position of theroller surface in contact with the tyre tread, when the roller is in theactive position, in a particularly easy and precise manner.

In an example embodiment, the processing unit is programmed to acquireat least one further pair of values, comprising a further radial forcevalue and a corresponding further value of the geometrical parameter.The processing unit is programmed to calculate at least one value of anelasticity parameter, representing the elasticity of the wheel to radialflattening, by comparing the pair of values with the further pair ofvalues.

It should be noted that calculating the elasticity parameter allows,with a limited number of measurements, finding the trend of thegeometrical parameter as a function of the force applied by the rollerto the tyre. This solution also allows extrapolating a value of thegeometrical parameter at a maximum radial force in a particularly sureand reliable manner.

The removal tool is movable. together with its supporting structureconnected to a column of the machine frame, for rotating about a sixthaxis parallel to the first axis and spaced from it. The rotation of theremoval tool relative to the sixth axis parallel to the axis of thewheel-holder unit allows the removal tool to be moved by rotationbetween a first position, proximal to the first axis (wherein theremoval tool may be positioned in contact with the tyre), and a secondposition, distal from the first axis (wherein the removal tool is in aposition of non-interference relative to the wheel).

Moreover, the removal tool is movable, preferably by translation, in adirection parallel to the first axis (that is, the axis of rotation ofthe wheel-holder unit).

The removal tool is movable, preferably by translation, towards and awayfrom the sixth axis (around which the supporting structure of theremoval tool rotates).

This allows the removal tool and, alternately, the roller, to be movedfrom a working position to a position of non-interference with thewheel, in a particularly fast and effective manner, without taking upthe space around the wheel.

In another embodiment according to this disclosure, a locking device isprovided for fixing the wheel to the wheel-holder unit, which guaranteesat the same time robustness and precision. This, for example, allows theroller to be used on a tyre changer machine with the taking ofparticularly precise measurements, without adversely affecting therobustness and reliability of the machine during the removal, fittingand bead breaking operations.

The device for locking a rim of a wheel is designed for fixing the rimof the wheel to a wheel-holder unit equipped with a supporting plate anda hollow rotary shaft; the hollow rotary shaft has an end portion whichprojects in a cantilever fashion from the supporting plate.

The locking device comprises a centring cone having a through hole.

Moreover, the locking device comprises a clamping rod having at a firstend and a second end. The clamping rod has, at its first end, a clampingelement which can be inserted inside the hollow shaft to prevent amovement of the clamping rod along the axis of the wheel-holder unit(for example, by a shape coupling, for example of the leaf spring type).The clamping rod has, at its second end, a portion coupled to a clampingelement. The clamping rod is elongate along a respective axis (which, inuse, coincides with the axis of rotation of the wheel-holder unit).

The clamping element is movably coupled to the portion of the clampingrod in such a way as to be moved along the axis of the clamping rod. Forexample, the portion of the clamping rod is threaded and the clampingelement can be rotated for translating along the axis of the clampingrod; it should be noted that there are different means of coupling, forexample by grooves, racks or other systems of substantially known type.

Moreover, the locking device comprises a centring flange. Operatively,the centring flange is interposed between the centring cone and theclamping element. The centring flange has a central through hole. Thecentring flange has a first face and a second face. The centring flangecomprises a plurality of centring rods projecting from the second face.The centring rods can be inserted in corresponding radial openings ofthe rim.

The first end of the clamping rod can be inserted in the hole of thecentring flange, with the same direction as that in which the centringrods project, and in the hole of the centring cone, with the oppositedirection to that along which the centring cone is tapered.

In that way, when the clamping element is operated, the flange ispressed towards the wheel-holder unit, so that the rim (the flange ofthe rim) is pressed against the centring cone. This ensures a centringand a locking of the wheel on the wheel-holder unit.

The centring is particularly precise because the portion of flange incontact with the cone is that characterised by greater precision (withreference to the manufacturing tolerances and the conditions of wear).

Preferably, the centring cone rests on a zone of the supporting platedesigned to oscillate parallel to the axis of the wheel-holder unit andwith a spring-like action. This makes it possible to apply aparticularly high clamping force without risk of ruining the rim.

In another embodiment, this disclosure provides a wheel service machinewhich can provide diagnostic information on the wheel which isparticularly complete and significant.

In one example embodiment, the processing unit is connected to a driveunit of the wheel-holder unit to measure a wheel rotation speedparameter. The processing unit is programmed to derive, from ageometrical parameter value calculated at a first rotation speed, amodified geometrical parameter value calculated at a second rotationspeed, as a function of data of a model representing a trend of theelasticity parameter as a function of the speed parameter.

Preferably, the processing unit is programmed to process a first valueof the geometrical parameter, corresponding to a first rotation speed,and a second value of the geometrical parameter, corresponding to asecond rotation speed, in order to derive at least one value of a firstmodelling parameter representing a variation of the geometricalparameter as a function of the rotation speed.

It should be noted that this solution allows extrapolating a value ofthe geometrical parameter at a predetermined rotation speed withouttaking the measurement. It should be noted that this solution enhancesmachine flexibility.

In an example embodiment, the processing unit is connected to a pressuresensor to measure a tyre inflation pressure parameter. The processingunit is programmed to derive, from a first value of the geometricalparameter calculated at a first inflation pressure, a modified value ofthe geometrical parameter at which the geometrical parameter adopts apredetermined or user set value.

Preferably, the processing unit is programmed to process a first valueof the geometrical parameter at a first inflation pressure and a secondvalue of the geometrical parameter at a second inflation pressure inorder to derive data representing a trend of the geometrical parameteras a function of the inflation pressure.

It should be noted that this solution allows extrapolating a value ofthe geometrical parameter at a predetermined inflation pressure withouttaking the measurement. It should be noted that this solution enhancesmachine flexibility.

It should also be noted that this solution allows the tyre servicespecialist to know the effect of the inflation pressure on thegeometrical parameter. Thus, the tyre service specialist can act on theinflation pressure to obtain a predetermined value of the geometricalparameter.

In an example embodiment, the processing unit is connected to an angularposition sensor to receive a signal representing the angular position ofa wheel mounted on the wheel-holder unit. The processing unit isprogrammed to acquire a plurality of values of the radial forceparameter as a function of an angular position of the wheel about thefirst axis, in order to calculate a radial force value averaged relativeto a predetermined angle of rotation imparted to the wheel about thefirst axis.

Preferably, the processing unit is configured to receive a signalrepresenting radial force during a wheel rotation and has access to avalue of an elasticity parameter representing the elasticity of thewheel to radial flattening. Preferably, the processing unit is alsoconfigured to derive an eccentricity parameter as a function of thatsignal and elasticity parameter.

It should be noted that this solution provides the tyre servicespecialist with information representing wheel eccentricity, thus givingthe tyre service specialist information which is more complete anduseful for diagnostic purposes.

In an example embodiment, the processing unit is configured to processdata relating to at least one control parameter for four wheels of avehicle. The processing unit is programmed to suggest an ameliorativeconfiguration as a function of that control parameter, where theameliorative configuration refers to one or more of the followingoptions:

-   -   positioning of the wheels on a vehicle;    -   coupling of a tyre to a wheel rim;    -   relative angular position of a tyre relative to a wheel rim.

According to the disclosure, the control parameter is one of theparameters from the following list:

-   -   geometrical parameter;    -   wheel eccentricity;    -   tyre tread depth;    -   wheel conicity.

In an example embodiment, the control unit is programmed to compare, foreach simple combination of wheels taken two at a time, the controlparameters relating to each wheel in order to obtain an analysisparameter. The control unit is programmed to identify at least one pairof wheels which minimizes the analysis parameter.

A further aim of this description is to provide a method for performingdiagnostic assessment of a vehicle wheel, in a wheel service machine,comprising the following steps:

-   -   rotating the wheel about a first axis;    -   positioning a roller, whose axis of rotation is parallel to the        first axis, in contact with the wheel tyre tread to apply a        predetermined radial force;    -   acquiring at least one force parameter representing a radial        force transmitted to the roller by the tyre;    -   acquiring at least one position parameter representing a        position of the roller relative to the first axis;    -   processing the position parameter to calculate at least one        value of a geometrical parameter representing a distance between        the first axis and a surface of the roller in contact with the        tyre tread and to derive a pair of values comprising a value of        the radial force measured by the force sensor when the roller is        in the active position and a corresponding value of the        geometrical parameter calculated.

In an example embodiment, the method comprises the following steps:

-   -   repositioning the roller in contact with the wheel tyre tread to        apply a second predetermined radial force;    -   acquiring at least one further force parameter representing a        radial force transmitted to the roller by the tyre;    -   acquiring at least one further position parameter representing a        position of the roller axis relative to the first axis;    -   processing the further position parameter to calculate at least        one value of a further geometrical parameter representing a        distance between the first axis and a surface of the roller in        contact with the wheel tyre tread and to derive a further pair        of values;    -   calculating at least one value of an elasticity parameter,        representing the elasticity of the wheel to radial flattening,        by comparing the pair of values with the further pair of values.

If the processing unit is connected to the drive unit of thewheel-holder unit to measure a wheel rotation speed parameter, themethod for performing diagnostic assessment of a vehicle wheel comprisesthe following steps:

-   -   acquiring at least one speed parameter representing a first        rotation speed of the wheel mounted on the wheel-holder unit;    -   calculating, from a geometrical parameter value calculated at        the first rotation speed, a modified geometrical parameter value        calculated at a second rotation speed, as a function of data of        a model representing a trend of the geometrical parameter as a        function of the speed parameter.

If the processing unit is connected to a pressure sensor to measure atyre inflation pressure parameter, the method for performing diagnosticassessment of a vehicle wheel comprises the following steps:

-   -   acquiring a tyre inflation pressure parameter representing a        first tyre inflation pressure;    -   calculating, from a value of the geometrical parameter        calculated at the first inflation pressure, a modified pressure        parameter value at which the geometrical parameter adopts a        predetermined or user set value.

It should be noted that this description provides a method for assistingthe tyre service specialist, comprising the following steps:

-   -   preparing four wheels;    -   measuring, for each wheel, a control parameter representing a        property of the wheel;    -   processing the control parameters for each simple combination of        wheels taken two at a time to obtain an analysis parameter for        each simple combination;    -   mounting on a front axle of a vehicle a pair of wheels which        minimizes the analysis parameter.

Preferably, the control parameter represents one of the wheel propertiesfrom the following list:

-   -   conicity;    -   eccentricity;    -   tread depth;    -   geometrical parameter.

According to one aspect of the present disclosure, the roller is movable(preferably, but not necessarily, by rotation) towards and away from thefirst axis between an active position, where it is in contact with atyre tread of a wheel mounted on the wheel-holder unit, to anon-interference position relative to the tyre.

The wheel service machine comprises at least one force sensor connectedto the roller for detecting a first signal, representing a radial forcetransmitted to the roller by the tyre in a direction perpendicular tothe axis of the roller, and/or a second signal, representing a lateralforce transmitted to the roller by the tyre in a direction parallel tothe axis of the roller.

Preferably, the wheel service machine comprises a first force sensor,for detecting the first signal, and a second force sensor, for detectingthe second signal.

The force sensors are preferably load cells; alternatively they can beextensometers or other devices.

The wheel service machine also comprises a processing unit (comprising aprocessor, for example, an electronic card suitably programmed)connected to the force sensors to receive the signals and process them.

Moreover, the wheel service machine comprises a distance sensor(preferably a laser sensor, alternatively an ultrasound sensor or otherdevice); the distance sensor is preferably a distance sensor withoutcontact.

The distance sensor is movable along an axis parallel to the first axis.

The distance sensor is configured for scanning a profile of the wheel(rim and the tyre) mounted on the wheel-holder unit.

The processing unit is connected to the distance sensor to receive ameasurement signal from it and programmed to compare the measurementsignal detected by the distance sensor with the signal detected by atleast one of the first and second load cells.

Preferably, the signals detected by the force sensors are acquired in asynchronous fashion relative to the distance sensor, relative to therotation of the wheel-holder unit simultaneous with the acquisition.

Preferably, the machine comprises an encoder or another sensor fordetecting a signal representing the angular position of the wheel-holderunit. The sensor is connected to the processing unit, which acquires thesignal simultaneously to the signals of the force sensors and to that ofthe distance sensor. Preferably, the position signal of the wheel-holderunit is used to synchronise the signals of the force sensors relative tothe signal of the distance sensor.

The comparison of the signals detected by the force sensors of theroller and the signals detected by the position sensor providesparticularly significant information from the diagnostics point of view,since this data is surprisingly complementary from the point of view ofdiagnostic importance.

More specifically, the first force signal is combined or compared with asignal of a measurement of eccentricity of the tyre (obtained with thedistance sensor at a fixed level, during rotation of the wheel).

On the other hand, the first force signal is combined or compared with asignal of a measurement of conicity of the tyre (obtained during amovement of the distance sensor parallel to the axis of rotation of thewheel, during rotation of the wheel).

BRIEF DESCRIPTION OF DRAWINGS

This and other features of the disclosure will become more apparent fromthe following detailed description of a preferred, non-limiting exampleembodiment of it, with reference to the accompanying drawings, in which:

FIG. 1 shows a first perspective view of a wheel service machineaccording to this description, where a wheel is mounted on thewheel-holder unit, and where the roller is in a non-interferenceposition;

FIG. 2 shows a second perspective view of a wheel service machineaccording to this description, where the roller is in a non-interferenceposition;

FIG. 3 shows a perspective view of an enlargement of the constructiondetail X from FIG. 1, according to this description;

FIG. 4 shows a first perspective view, with some parts cut away tobetter illustrate others, of a wheel service machine, according to thisdescription, where the roller is in an active position;

FIG. 5 shows a second perspective view, with some parts cut away tobetter illustrate others, of a wheel service machine, according to thisdescription, where the roller is in an active position;

FIG. 6 shows a perspective view of an enlargement of the constructiondetail Y from FIG. 4, according to this description;

FIG. 7 shows a side cross sectional view, with some parts cut away tobetter illustrate others, of a wheel-holder unit of the wheel servicemachine of FIG. 1, according to this description;

FIG. 8 shows a perspective view, with some parts cut away to betterillustrate others, of a detail of the wheel-holder unit of the wheelservice machine of FIG. 1, according to this description;

FIG. 9 shows a side view, with some parts cut away to better illustrateothers, of the wheel-holder unit of the wheel service machine of FIG. 1,according to this description;

FIG. 10 shows a cross section, with some parts cut away to betterillustrate others, of the detail of the wheel-holder unit of FIG. 9,according to this description;

FIG. 11 shows a first perspective view, with some parts cut away tobetter illustrate others, of the wheel-holder unit of the wheel servicemachine of FIG. 1, according to this description;

FIG. 12 shows a second perspective view, with some parts cut away tobetter illustrate others, of a detail of the wheel-holder unit of thewheel service machine of FIG. 1, according to this description;

FIG. 13 shows a first perspective view of a variant embodiment of acentring flange according to this description;

FIG. 14 shows a second perspective view of the centring flange of FIG.13 according to this description;

FIG. 15 shows a perspective view of a variant embodiment of a centringflange according to this description.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

With reference to the accompanying drawings, the numeral 1 denotes awheel service machine. More specifically, in the embodiment illustrated,the numeral 1 denotes a machine for fitting and removing a tyre to/froma corresponding vehicle wheel rim (that is, a tyre changer) comprising aload roller 2, according to this description.

The machine 1 comprises a frame. Preferably, the frame comprises a base3. The base 3 comprises a wheel-holder unit 4. The wheel-holder unit 4is designed to fix the wheel by means of a locking device and to rotateit about an axis of rotation A. Preferably, the first axis of rotation Ais vertical.

Preferably, the base 3 comprises a mechanism 5 for lifting the wheel, ofknown type.

The wheel-holder unit 4 comprises a supporting shaft 6 having a firstand a second end. The first end of the supporting shaft 6 is connectedto rotation means 7. The second end of the supporting shaft 6 isconfigured for coupling to a supporting apparatus 8, moving as one inthe rotational movement about the first axis A.

In the embodiment illustrated, the rotation means 7 comprise a driveunit 7 a connected to a drive wheel. The drive wheel is connected to awheel driven by a transmission belt. The driven wheel rotates atransmission shaft 7 b which has a threaded portion, configured forcoupling to a gear wheel 7 c. The gear wheel 7 c is coupled to thesupporting shaft 6, preferably by a key 7 d (or a tab). The supportingshaft 6 is mounted on bearings 9. Preferably, the bearings 9 are taperedroller bearings.

Preferably, the base 3 comprises a first pedal. A user can set thewheel-holder unit 4 in rotation by acting on the first pedal.

The supporting apparatus 8 has a supporting plate 12, which defines aplane perpendicular to the first axis A. The supporting plate 12 has anaxial hole to allow a clamping tool (or rod) 11, of known type, to passthrough.

The supporting plate 12 comprises a first annular element 12 b (that is,a movable annular element 12 b) and a second annular element 12 a (thatis, a fixed annular element 12 a). Preferably, the first annular element12 b and the second annular element 12 a are concentric. The secondannular element 12 a is situated at a greater radial distance from thefirst axis A than the first annular element 12 b.

Preferably, the fixed annular element 12 a has a plurality of radialgrooves 12 c. Even more preferably, the fixed annular element 12 a hasthree radial grooves 12 c which are angularly equidistant.

The supporting apparatus 8 comprises a hollow shaft, to allow theclamping rod 11 to pass through, having an end portion which projectscantilever-style from the supporting plate 12, at its axial hole. Itshould be noted that the hollow shaft constitutes an extension of thesupporting shaft 6, in the direction of the first axis A and away fromthe base 3. The hollow shaft rotates as one with the supportingapparatus 8 about the first axis A. Preferably, the first annularelement 12 b is connected to the outer surface of the hollow shaft so asto be movable in a direction parallel to the first axis A. Preferably,the movable annular element 12 b of the supporting plate 12 of thewheel-holder unit 4 has at least one tooth 14 b slidably coupled to agroove 14 a defined by the hollow shaft and oriented parallel to thefirst axis A of the wheel-holder unit 4.

In the embodiment illustrated, the supporting apparatus 8 comprises ashaped bushing 14, inserted in the hole of the supporting plate 12 andconfigured for guiding the clamping rod 11 during insertion. The shapedbushing 14 extends, in the direction of the first axis A, beyond theplane defined by the supporting plate 12, in a direction away from thebase 3.

In the embodiment illustrated, a supporting ring 15 is connected to aninner portion of the movable annular element 12 b. The supporting ring15 is coupled to the shaped bushing 14 for guiding the movable annularelement 12 b in a direction parallel to the first axis A. Preferably,the shaped bushing 14 has a groove 14 a, which extends in a directionparallel to the first axis A. Preferably, the movable annular element 12b is coupled to the shaped bushing 14 by the at least one tooth 14 b,having an end inserted in the groove 14 a.

The clamping rod 11 is formed by a longitudinal shaft having a first anda second end. The first end of the clamping rod 11 has a locking element10 which can be inserted inside the hollow shaft to prevent a movementof the clamping rod 11 along the first axis A. In the embodimentillustrated, the first end of the clamping rod 11 is shaped to becoupled to the supporting apparatus 8 by a shape coupling 18 which,after being formed, prevents the clamping rod 11 from moving in thedirection of the first axis A. Preferably, the shape coupling is abayonet or key-type coupling.

The second end of the clamping rod 11 has a handgrip 11 a and isconnected to a clamping element 17 (of known type) by a threadedportion. The clamping element 17 is coupled to the threaded portion ofthe clamping rod 11 and can be rotated, in such a way as to move along adirection parallel to the first axis A.

It should be noted that, according to this embodiment, the hollow shaftis therefore defined by the zone between one end of the shaped bushing14, which is distal from the base 3, and the shape coupling 18.

The supporting apparatus 8 also comprises an elastic element 13,connected to the movable annular element 12 b and configured to generatea force along a direction parallel to the first axis of rotation A in adirection away from the base 3, when the movable annular member 12 b ispushed in a direction parallel to the first axis A towards the base 3.In the embodiment illustrated, the elastic element 13 is interposedbetween the movable annular element 12 b and a plate 8 a in thesupporting apparatus 8 and positioned perpendicularly to the first axisA.

The locking device comprises a centring cone 16, having a through hole.The through hole allows the centring cone 16 to be coupled to the endportion of the shaped bushing 14 (that is, of the hollow shaft)projecting in cantilever fashion from the supporting plate 12. It shouldbe noted that the movable annular element 12 b defines a supportingsurface for receiving and supporting the centring cone 16. Preferably,the supporting surface is defined by the supporting ring 15.

Preferably, the centring cone 16 is tapered from a first enlarged end toa second narrow end and comprises an annular protrusion 16 a which issmaller in diameter than the first enlarged end and which projects fromthe first end away from the second end.

The machine 1 according to this disclosure comprises an anti-rotationsystem to prevent the rim mounted on the wheel-holder unit 4 fromrotating relative to the supporting plate 12. The anti-rotation systemcomprises an anti-rotation pin 19 oriented parallel to the first axis Aof the wheel-holder unit 4 and projecting in the same direction as theend portion of the hollow shaft projecting in a cantilever fashion fromthe supporting plate 12. Preferably, the anti-rotation pin 19 isconnected to one end of a shaped arm 20 which rotates about an axisparallel to the first axis A of the wheel-holder unit 4, for varying adistance of the anti-rotation pin 19 relative to the first axis A of thewheel-holder unit 4.

Preferably, the second end of the shaped arm 20 is coupled to acylinder-piston system 21, which defines a hinged coupling to allow theshaped arm 20 to rotate about an axis parallel to the first axis ofrotation A. The cylinder-piston system 21 also comprises a spring 22,configured to allow the shaped arm 20 and the anti-rotation pin 19 tomove in a direction parallel to the first axis A and to apply on theshaped arm 20 a force in a direction parallel to the first axis ofrotation A, in the direction away from the base 3, when the shaped arm20 is pushed towards the base 3.

A centring flange 23 comprises a plate 23 a. The plate 23 a comprises afirst face 23 e, a second face 23 f and a central through hole. Two ormore centring rods 23 b, which can be inserted into corresponding radialopenings of the rim, project from the second face 23 f of the plate 23 ain a cantilever fashion.

The two or more centring rods 23 b, having an elongate shape in adirection perpendicular to a plane defined by the plate 23 a, areequidistant from each other. In other words, the intersections betweenthe directions in which the two or more centring rods 23 b extend andthe plane defined by the plate 23 a define a plurality of points locatedat the vertices of an equilateral polygon.

Preferably, the two or more centring rods 23 b are movable towards andaway from the hole of the centring flange 23.

Preferably, at least one of the two or more centring rods 23 b of thecentring flange 23 forms a recess (that is, a coupling hole 23 h) on anend surface of it, to receive the anti-rotation pin 19 oriented parallelto the axis of the hole of the centring flange 23 (that is, parallel tothe first axis A). In a further embodiment, at least one of the two ormore centring rods 23 b of the centring flange 23 forms a coupling pin23 i.

Preferably, the two or more centring rods 23 b are positioned along acircumference, equispaced from each other around the central hole of thecentring flange 23 and are kinematically interconnected with each otherby means of a gear assembly.

In the embodiment illustrated, a plurality of pinions 23 c is positionedon the second face 23 f of the plate 23 a. Each pinion 23 c rotatesabout its axis of rotation, perpendicular to a plane defined by theplate 23 a. The plurality of pinions 23 c is coupled to a crown 23 d,for rotating simultaneously by the same angle.

Each of the two or more centring rods 23 b comprises a first and asecond end. The first end of the centring rod 23 b is fixed to theperiphery of a pinion 23 c In other words, each of the two or morecentring rods 23 b is fixed to a respective pinion 23 c. In this way, itis possible to increase or reduce the distance between the centring rods23 b, which remain, however, equidistant from each other.

Preferably, the second end of each of the two or more centring rods 23 bis bevelled for coupling with a corresponding radial opening of the rim.

The first face 23 e of the plate 23 a has at least one coupling element23 g, designed to be inserted in a seat formed on the surface of thesupporting plate 12. In the embodiment illustrated, the coupling element23 g is configured to be inserted in a groove 12 c of the fixed annularelement 12 a.

When the machine 1 operates on a rim with an inverted channel, thecentring flange 23 is positioned on the supporting apparatus 8 in such away that the first face 23 e of the plate 23 a is in contact with thesupporting plate 12, and the centring rods 23 b protrude in a directionparallel to the first axis A, in a direction away from the base 3. Inthis way, the coupling element 23 g fits into a radial groove 12 c andprevents rotation of the centring flange 23 when the machine 1 operateson a rim with an inverted channel.

In the embodiment illustrated, the frame of the machine 1 comprises acolumn 24 associated with the base 3. The column 24 extends preferablyin a direction parallel to the first axis A. Preferably, the column 24extends vertically.

The column 24 comprises a guide 25 extending along the main direction ofextension of the column 24. A first carriage 26 is slidably constrainedto the guide 25 to move along the guide 25 upwards or downwards.

A first movement system is associated with the first carriage 26 withthe purpose of moving the first carriage 26 between a first upper endposition and a second lower end position along the guide 25.

The first movement system associated with the first carriage 26comprises a first actuator 27.

A first arm 28 has a first and a second end. The first end of the firstupper arm 28 is coupled to the first carriage 26. More specifically, thecoupling is such as to allow the first arm 28 to move in a directionperpendicular to the first axis of rotation A. The second end of thefirst arm 28 is connected to a first bead breaker tool 29. That way, thebead breaker tool 29 is movable along a second axis B parallel to thefirst axis A. The coupling between the first carriage 26 and the guide25 is such as to allow the first carriage 26 to rotate about a thirdaxis C, preferably parallel to the first axis of rotation A, to allowthe first bead breaker tool 29 to pass from an active position, wherethe second axis B intersects the wheel mounted on the wheel-holder unit,to a deactivated position, where the second axis B is spaced from thewheel.

A second carriage 30 is slidably constrained to the guide 25 to movealong the guide 25 upwards or downwards. A second movement system isassociated with the second carriage 30 to move the second carriage 30between a first lower end position and a second upper end position alongthe guide 25. Preferably, the first carriage 26 and the second carriage30 are slidably connected to the guide 25.

The second movement system associated with the second carriage 30comprises a second actuator 31. A second arm 32 has a first and a secondend. The first end of the second arm 32 is fixed to the second carriage30. More specifically, the coupling is such as to allow the second arm32 to move in a direction perpendicular to the first axis of rotation A.The second end of the second arm 32 is connected to a second beadbreaker tool 33. Preferably, the bead breaker tools 29,33 are bothmovable along the second axis B. Preferably, the coupling between thesecond carriage 30 and the guide 25 allows the second carriage 30 torotate about the third axis C. It should be noted that if there are twobead breaker tools (and not only one) they both rotate about the axis Cor, alternatively, only one rotates.

The bead breaker tools 29,33 may therefore be moved towards or away fromthe axis of the wheel-holder unit, allowing the machine 1 to operate ontyres of different diameters. Each bead breaker tool 29,33 comprises acircular body supported by a supporting arm. The circular body isconfigured to press one tyre bead towards the opposite bead in order todetach it from the corresponding edge of the rim. The coupling betweenthe circular body and the supporting arm allows the circular body torotate in contact with the wheel when located in a working position.

The roller 2 of the machine 1 rotates about a fourth axis D. The roller2 is movable towards and away from the wheel-holder unit 4 along anoperating trajectory such that the axis of the roller remains parallelto the first axis A. The roller 2 is movable between a position ofnon-interference with the tyre of a wheel mounted on the wheel-holderunit 4 and an active position where it applies a predetermined force tothe tyre tread.

The roller 2 is movably connected to the frame by means of a connectingstructure. In the embodiment illustrated, the connecting structurecomprises an articulated arm 38 having a first and a second end. Thefirst end of the articulated arm 38 is coupled to the column 24 torotate about a fifth axis E. Preferably, the fifth axis E is parallel tothe first axis A.

The second end of the articulated arm 38 is coupled to the roller 2. Thecoupling between the articulated arm 38 and the column 24 allows theroller 2 to be moved towards the tyre of the wheel mounted on thewheel-holder unit 4, by rotating the articulated arm 38 about the fifthaxis E. In other words, the rotation of the articulated arm 38 about thefifth axis E allows the roller 2 to be moved from a position ofnon-interference relative the tyre to an active position, where it is incontact with the tyre tread.

Preferably, the movement of the roller 2 between the active position andthe non-interference position, and vice versa, is performed by means ofa third actuator 36. Preferably, the third actuator 36 is a linearactuator or a worm screw which allows the roller to be locked in theactive position.

The roller 2 comprises a protective shell 39, which covers a portion ofthe lateral surface of the roller 2, and is configured to prevent anyaccidents to the tyre service specialist due to contact with the roller2 during its use. The protective shell comprises a contact element 39 a,configured to make contact with the tyre tread without interfering withthe functions of the latter. Preferably, the contact is of a sliding orrolling type. The protective shell is pivoted to the articulated arm 38to rotate about an axis preferably parallel to the fourth axis D and toadapt to wheels having different diameters.

The roller 2 is equipped with a first force sensor 40 for measuring aradially directed force applied by the tyre to the roller. Preferably,the first force sensor 40 is coupled to the articulated arm 38.

Preferably, the roller 2 is equipped with a second force sensor 45, formeasuring an axially directed force applied by the tyre to the roller.Preferably, the sensors 40, 45 are load cells or extensometers.

The machine 1 comprises a supporting arm 34 having a first and a secondend. The first end of the supporting arm 34 is coupled to the column 24.More specifically, the coupling allows the supporting arm 34 to rotateabout a sixth axis F. Preferably, the sixth axis F is parallel to thefirst axis A. Preferably, the supporting arm 34 is configured to extendin a direction perpendicular to the first axis of rotation A.

The second end of the supporting arm 34 is coupled to a tool holder arm35 having a first and a second end. Preferably, the tool holder arm 35is telescopic.

The first end of the tool holder arm 35 is coupled to a fourth actuator46, for moving in a direction parallel to the first axis of rotation A.The second end of the tool holder arm 35 is connected to a removal tool37. Preferably, the removal tool 37 is connected to a fifth actuator 47,which controls its movement while the tyre is being removed from/fittedto the rim. More specifically, the removal tool 37 is configured toswing about an axis in a direction perpendicular to the first axis A,and in a direction perpendicular to the direction in which thesupporting arm 34 is configured to extend.

The removal tool 37 is positioned relative to the wheel-holder unit 4 torotate from the active position to the non-interference position aboutthe sixth axis F in a first direction of rotation. Preferably, the beadbreaker tools 29,33 are positioned relative to the wheel-holder unit 4to rotate from the active position to the non-interference positionabout the third axis C in a second direction of rotation, opposite thefirst direction of rotation. Preferably, the roller 2 is positionedrelative to the wheel-holder unit 4 to rotate from the active positionto the non-interference position about the fifth axis E in the firstdirection of rotation.

Preferably, the fourth actuator 46 is configured to allow intermediatepositions of stable equilibrium between end of stroke limit positions. Afirst control unit 41, connected to the fourth actuator 46, definesthree operating configurations: a first operating configuration in whichit drives the fourth actuator 46 into a retracted limit stop position,to move the removal tool 37 away from the wheel-holder unit 4, a secondoperating configuration in which it drives the fourth actuator 46 so asto extract it to an extracted limit stop position, to move the removaltool 37 towards the wheel-holder unit 4, a third operating configurationin which it stops the fourth actuator 46 in a position intermediatebetween the retracted limit stop position and the extracted limit stopposition, stopping the removal tool 37 in a position adopted at theinstant of activation of the first control unit 41.

Preferably, the supporting arm 34 can be moved manually, in thedirection in which it extends, by means of a first handle 44. The firsthandle is located preferably in the proximity of the first control unit41 so that a user can actuate the first control unit 41 by holding thefirst handle 44.

The machine 1 comprises a locking mechanism, which can be operated by asecond control unit 42, configured to block the movement of the removaltool 37 towards and away from the sixth axis F, without limitingmovement of the tool along the direction parallel to the first axis Aand rotation about the sixth axis F.

Preferably, the machine 1 also comprises a sixth actuator, connected tothe supporting arm 34 to rotate it about the sixth axis F between anactive angular position and a passive angular position. The sixthactuator is configured to allow two positions of stable equilibriumcorresponding to a first and a second end of stroke limit position. Theremoval tool 37 is located at a first position, proximal to the firstaxis A, when the supporting arm 34 is in the active angular position,and in a second position, distal from the first axis A, when thesupporting arm 34 is in the passive angular position.

Preferably, the supporting arm 34, when in the active angular position,is oriented along an axis intersecting the first axis A.

The machine 1 according to this disclosure comprises a processing unit.The processing unit is connected to the first force sensor 40 foracquiring the values of a first force parameter, representing a radialforce transmitted to the roller 2, and processing them. The processingunit is connected to the second force sensor 45 for acquiring the valuesof a second force parameter, representing an axial force transmitted tothe roller 2, and processing them.

Preferably, the machine 1 comprises a contactless distance sensor 43.Preferably, the distance sensor 43 is a laser sensor or an ultrasoundsensor. The distance sensor 43 is movable along an axis parallel to thefirst axis A and is configured to scan a profile of the wheel mounted onthe wheel-holder unit 4. Preferably, the distance sensor 43 is coupledto the column 24 by a slide 48.

The processing unit is connected to the distance sensor to receive ameasurement signal from it and programmed to compare the measurementsignal detected by the distance sensor 43 with a signal detected by atleast one of the force sensors 40,45. Preferably, the processing unit isconnected to an angular position sensor to receive a signal representingthe angular position of the wheel-holder unit 4. Preferably, theprocessing unit is connected to the third actuator 36 to enable orprevent its activation as a function of a position of the liftingelement and/or a position of the removal tool 37. Preferably, theprocessing unit is connected to the third actuator 36 to enable theactivation thereof to cause the roller 2 to move close to thewheel-holder unit during rotation of the wheel on the wheel-holder unit4. Preferably, the processing unit is connected to the third actuator 36to enable the activation thereof to cause the roller 2 to move away fromthe wheel-holder unit 4 when the wheel on the wheel-holder unit 4 stopsrotating.

Preferably, the processing unit is programmed to acquire in asynchronized fashion a measurement signal detected by the distancesensor 43 and a signal detected by at least one of the force sensors40,45 in order to derive a succession of pairs of values of the signals,where each pair of values relates to a same angular position of thewheel-holder unit 4

Preferably, the processing unit is also programmed to acquire in asynchronized fashion a measurement signal detected by the distancesensor 43, positioned in a stationary position, and a signal detected bythe first force sensor 40, in order to derive a succession of pairs ofvalues of the signals, where each pair of values relates to a sameangular position of the wheel-holder unit 4 and a same position of thedistance sensor 43.

Preferably, the processing unit is programmed to acquire in asynchronized fashion a measurement signal detected by the distancesensor 43 during a movement thereof along an axis parallel to the firstaxis A and a signal detected by the second force sensor 45, in order toderive a succession of pairs of values of the signals, where each pairof values relates to a same angular position of the wheel-holder unit 4.

Preferably, the processing unit is programmed to develop in Fourierseries a signal detected by the force sensors 40,45 and a measurementsignal detected by the distance sensor 43, to calculate one or morediagnostic parameters given by the ratio of the Fourier seriescoefficients relating to corresponding harmonics.

Preferably, the processing unit is programmed to develop in Fourierseries a signal detected by the first force sensor 40 and a measurementsignal detected by the distance sensor 43, synchronized with each other,to calculate one or more diagnostic parameters given by the ratio of theFourier series coefficients relating to corresponding harmonics.

Preferably, the processing unit is programmed to develop in Fourierseries a signal detected by second force sensor 45 and a measurementsignal detected by the distance sensor 43, synchronized with each other,to calculate one or more diagnostic parameters given by the ratio of theFourier series coefficients relating to corresponding harmonics.

Preferably, the processing unit comprises a memory configured to storedata and signals from the sensors of the machine 1.

With regard to the operations for removing and fitting the tyre from/toa corresponding wheel rim, attention is drawn to the following.

According to this disclosure, the machine 1 is able to perform theoperations both for removing and fitting the tyre on the correspondingrim. Preferably, the removal tool 37 is configured to perform both theoperations.

The machine 1 also provides the tyre service specialist with the loadroller 2. The roller 2, which rotates about the fourth axis D, parallelto the first axis A, is rotated about a fifth axis E spaced from thefourth axis D, between a non-interference position relative to the tyreand an active position, where it is in contact with the tyre tread ofthe wheel mounted on the wheel-holder unit 4 to apply a predeterminedforce on the tyre tread.

The rotation of the wheel-holder unit 4 and the wheel fixed to it makesit possible to measure a plurality of values of forces applied to theroller 2 by the tyre as a function of its angular position. The rotationof the wheel-holder unit 4 is stopped upon completion of the measurementand the roller 2 is returned to the non-interference position.

To proceed to removal operations, it is necessary to fix the wheel rimto the wheel-holder unit 4. The locking step will be described in moredetail below.

The detachment of a bead of the tyre from a corresponding annular edgeof the rim (that is, the “bead breaking” step) requires the activationby the tyre service specialist of the bead breaker tool 29. The beadbreaker tool 29 is movable along the second axis B, preferably parallelto the first axis A. The bead breaker tool 29 is also movable byrotation about the third axis C, from a deactivated position, where thesecond axis B is spaced from the wheel, to an active position, where thesecond axis B intersects the wheel mounted on the wheel-holder unit 4.Once the bead breaker tool 29 is positioned in contact with a side wallof the tyre, the bead is detached from the corresponding annular edge byrotating the wheel fixed to the wheel-holder unit 4.

The rotation of the wheel-holder unit 4 and of the wheel fixed to it isstopped upon completion of the bead breaking step (at this point, beadbreaking is completed).

It should be noted that the tyre has two beads. Preferably, to performthe bead breaking on a second bead the second bead breaker tool 33 isoperated, which is movable along the second axis B preferably parallelto the first axis A, and movable by rotation about the third axis C,from a deactivated position, where the second axis B is spaced from thewheel, to an active position, where the second axis B intersects thewheel mounted on the wheel-holder unit 4.

Preferably, the movement of the bead breaker tools 29,33 in thedirection of the second axis B is achieved by moving the first carriage26 and the second carriage 30 along the guide 25. Preferably, therotation of the bead breaker tools 29,33 about the third axis C occursthanks to the coupling of the first carriage 26 and the second carriage30 to the guide 25.

Preferably, at the end of bead breaking the bead breaker tools 29,33 aremoved to the deactivated position, where the second axis B is spacedfrom the wheel.

The tyre service specialist activates the removal tool 37, by rotatingit about the sixth axis F parallel to the first axis A and spaced fromit. Preferably, the supporting arm 34, driven by the sixth actuator,rotates about the sixth axis F from a passive angular position to anactive angular position. In the active angular position, the directionin which the supporting arm 34 extends intersects the first axis A.

The removal tool 37 is also moved in a direction parallel to the firstaxis A and in a direction perpendicular to the first axis A so as topass from a position of non-interference relative to the wheel to anactive position, where it is operatively active on the tyre.

Preferably, the tyre service specialist acts on the first control unit41, connected to the fourth actuator 46, positioning it in a secondoperating configuration in which it drives the actuator so it isextracted towards an extracted limit stop position, to move the removaltool 37 in a direction parallel to the first axis A, towards thewheel-holder unit 4. Preferably, during the movement of the removal tool37 in a direction parallel to the first axis A, the tyre servicespecialist acts on the first handle 44 to move the supporting arm 34 ina direction perpendicular to the first axis A, and improve thepositioning of the removal tool 37 relative to the wheel in a radialdirection.

After reaching the desired height, the tyre service specialist furtheracts on the first control unit 41, positioning it in a third operatingconfiguration, where it stops the fourth actuator 46. Preferably, themovement of the control unit in the third operating configuration blocksthe movement of the supporting arm 34 in the direction in which itextends and also blocks the movement of the tool holder arm 35 in thedirection parallel to the first axis A, to allow the removal operationsto be carried out.

To remove the tyre from the rim it is possible to rotate the supportingarm 34 to the passive angular position. To avoid interference with theroller 2, the tyre service specialist may act on the second control unit42, changing it from a first to a second operating configuration. Whenthe second control unit 42 is in the second operating configuration, thetyre service specialist may act on the first control unit 41 moving itto the first operating configuration, moving the removal tool 37 awayfrom the wheel-holder unit 4 whilst the position of the supporting arm34 remains locked along the direction in which it is extends. It is thuspossible to rotate the supporting arm 34 (that is, the removal tool 37)about the sixth axis F, without altering the distance of the removaltool 37 from the sixth axis F.

With regard to the operations for fixing the wheel (or the rim) to thewheel-holder unit 4, the tyre service specialist must couple thecentring cone 16 to the end portion of the hollow shaft, in such a waythat the centring cone 16 is tapered in the same direction as that inwhich the end portion of the hollow shaft extends.

In the embodiment in which the centring cone 16 has an annularprotrusion 16 a, the centring cone is positioned in such a way that theannular protrusion 16 a is in contact with the movable annular element12 b.

The rim is then positioned on the supporting plate 12, in such a waythat a central hole of the rim is coupled to the centring cone 16. Thecentring rods 23 b of the centring flange 23 are inserted in the radialopenings of the rim until the second face 23 f (at least a portion ofit) of the centring flange 23 is in contact with the rim. Next, thefirst end of the clamping rod 11, having a locking element 10, isinserted in the central hole of the rim and moved along the first axis Ain a direction towards the base 3. Inserting the locking element 10 ofthe clamping rod 11 inside the hollow shaft to form the shape coupling18 prevents further movement of the clamping rod 11 in a directionparallel to the first axis A.

The clamping element 17 is then operated, to move it along the clampingrod 11 until it presses on the first face 23 e of the centring flange 23to clamp it against the rim.

In the embodiment in which the supporting plate 12 comprises the movableannular element 12 b, elastically supported by the elastic element 13 sothat it can be moved in a direction parallel to the first axis A, thecentring cone 16 is positioned in contact with the movable annularelement 12 b of the supporting plate 12.

In the embodiment in which the wheel-holder unit 4 comprises ananti-rotation system to prevent relative rotation between the rimmounted on the wheel-holder unit 4 and the supporting plate 12, theanti-rotation pin 19, oriented parallel to the first axis A andprojecting in the same direction as the end portion of the hollow shaftprojecting in cantilever fashion from the supporting plate 12, iscoupled to one end of at least one of the centring rods 23 b of thecentring flange 23, which has a coupling hole 23 h.

According to another aspect of this description, a method for performingdiagnostic assessment of a vehicle wheel is also defined.

After fixing the wheel to the wheel-holder unit 4 the roller ispositioned in contact with the wheel tyre tread.

By rotating the wheel about the first axis A, the first force sensor 40detects a first signal representing a radial force imparted to theroller 2 by the tyre in a direction perpendicular to the fourth axis D.

The second force sensor 45 detects a second signal representing alateral force, imparted to the roller 2 by the tyre in a directionparallel to the fourth axis D.

The distance sensor 43, which is movable along an axis parallel to thefirst axis A and configured to scan a profile of the wheel, detects ameasurement signal. The processing unit receives the first and secondsignals and processes them, comparing at least one of them with themeasurement signal detected by the distance sensor 43.

Preferably, a third signal is detected by the distance sensor 43,positioned in a stationary position, during the rotation of the wheel,and acquired simultaneously with the first signal detected by the firstforce sensor 40, in such a way that the third and first signals areacquired in a synchronized fashion.

Preferably, a fourth signal is detected by the distance sensor 43 duringa movement of the latter parallel to the first axis A, during therotation of the wheel, and it is acquired simultaneously with the secondsignal detected by the second force sensor 45, in such a way that thethird and first signals are acquired in a synchronized fashion.

Preferably, processing by the processing unit comprises developing inFourier series the signal detected by at least one of the force sensors40,45 and of the measurement signal detected by the distance sensor 43,to calculate one or more diagnostic parameters given by the ratio of theFourier series coefficients relating to corresponding harmonics.

Preferably, processing by the processing unit comprises developing inFourier series the first and third signals and calculating one or morediagnostic parameters given by the ratio of the Fourier seriescoefficients relating to corresponding harmonics.

Preferably, processing by the processing unit comprises developing inFourier series the second and fourth signals and calculating one or morediagnostic parameters given by the ratio of the Fourier seriescoefficients relating to corresponding harmonics.

The machine 1 comprises a position sensor configured to measure valuesof a position parameter representing a position of the roller 2 relativeto the frame.

Preferably, the position sensor is coupled to the connecting structureat a predetermined position in order to detect a position of apredetermined zone of the connecting structure. Preferably, theprocessing unit holds in its memory information representing therelative position between the predetermined zone and the axis D of theroller 2.

If the connecting structure of the machine 1 comprises an articulatedarm 38 connected to the roller 2 in order to move the roller 2 byrotation about the fifth axis E, the position sensor is configured toderive a rotation of the articulated arm 38 relative to the frame.Preferably, the position sensor is an angular position transducer.

In an example embodiment, the processing unit contains data relating tothe geometrical dimensions of the machine 1 (relating in particular to alength of the articulated arm 38 and a radius of the roller 2) tocalculate a position of the fourth axis D based on trigonometricrelations.

According to an aspect of this disclosure, the processing unit isconfigured to calculate, as a function of the position parameter, ageometrical parameter representing a distance between the first axis Aand a surface of the roller 2 in contact with the tyre tread when theroller 2 is in the active position. In other words, the processing unitis programmed to derive a geometrical parameter indicating a flatteningof the roller 2 subjected to a predetermined radial force (or load).

The processing unit is also programmed to derive a pair of valuescomprising a value of the radial force measured by the first forcesensor 40 and a corresponding value of the geometrical parameter. Inother words, the processing unit is programmed to associate acorresponding value of the geometrical parameter with a radial loadvalue applied to the tyre tread.

Preferably, the processing unit is programmed to acquire at least onefurther pair of values in addition to the pair of values derived inrelation to the predetermined force applied by the roller 2 to the tyretread. The further pair of values comprises a further radial force valueand a corresponding further value of the geometrical parameter. Theprocessing unit is programmed to calculate at least one value of anelasticity parameter, representing the elasticity of the wheel to radialflattening, by comparing the pair of values with the further pair ofvalues.

The value of the geometrical parameter is affected by the radial loadapplied by the roller 2 to the tyre tread. Preferably, the processingunit is programmed to calculate a trend of the geometrical parameter asa function of the predetermined force applied by the roller 2.

More specifically, by taking at least two different radial loadmeasurements, it is possible to define at least two test points on agraph where a first Cartesian axis (or axis of abscissas) shows valuesof the predetermined force applied to the tyre by the roller 2 and asecond Cartesian axis (axis of ordinates) shows values of thegeometrical parameter, thus defining a radial force-geometricalparameter plane. The processing unit is programmed to calculate a firstangular coefficient of a straight line passing through the at least twotest points in the radial force-geometrical parameter plane. Based on ahypothesis of linearity, this angular coefficient is the elasticityparameter.

In a further example embodiment, the processing unit is configured tocalculate the elasticity parameter from a first plurality of test pointsin the radial force-geometrical parameter plane, for example bycalculating the coefficients of a linear regression.

If the hypothesis of linearity is not satisfied, the processing unit isprogrammed to calculate, by means of an iterative algorithm, a firstplurality of parametric coefficients of a first parametric function forinterpolating the first plurality of test points.

In an example embodiment, at least one test point of the first pluralityof test points corresponds to a value of the geometrical parameter inthe absence of a load. Preferably, this geometrical parameter iscalculated by the processing unit based on a measurement signal from thedistance sensor 43. In other words, the value of the geometricalparameter in the absence of a load is calculated using data from a tyreprofile scan by means of the distance sensor 43.

In an example embodiment, the processing unit is connected to theangular position sensor to receive a signal representing an angularposition of a wheel mounted on the wheel-holder unit 4. The processingunit is programmed to acquire a plurality of values of the radial forceparameter as a function of an angular position of the wheel about thefirst axis A, in order to calculate a radial force value averagedrelative to a predetermined angle of rotation imparted to the wheelabout the first axis A. In other words, the processing unit isconfigured to associate radial force values measured by the first forcesensor 40 with corresponding angular positions of the wheel relative tothe first axis A. Preferably, the processing unit is programmed toderive a radial force value averaged on a 360° angle of rotation of thewheel.

In an example embodiment, the processing unit is configured to receive asignal representing radial force during a rotation of the wheel and hasaccess to a memory containing at least one value of the elasticityparameter, to derive an eccentricity parameter as a function of thatsignal and that elasticity parameter. Preferably, the processing unit isprogrammed to calculate the eccentricity parameter by means of thefollowing relation:

${{R(\theta)} = {{R_{0} + {{dR}(\theta)}} = {\frac{F_{0}}{k} + \frac{{dF}(\theta)}{k}}}};$where R(θ is the eccentricity parameter at an angular position θ, R₀ isa nominal radius of a wheel, dR(θ) is a deviation of the wheel radiusfrom the nominal value R₀ at an angular position θ, F₀ is apredetermined value of radial force, dF(θ) is a deviation from thepredetermined value F₀ of a radial force measured by the first forcesensor 40 at an angular position θ, and k is the elasticity parameter.

In one example embodiment, the processing unit is connected to a driveunit 7 a of the wheel-holder unit 4 to measure a wheel rotation speedparameter.

In one example embodiment, the processing unit is programmed to derive atrend of the elasticity parameter as a function of the speed parameter.In other words, the processing unit is programmed to calculate avariation of the angular coefficient in the radial force-geometricalparameter plane as a function of the rotation speed of the wheel mountedon the wheel-holder unit 4.

Preferably, the processing unit is programmed to derive, from ageometrical parameter value calculated at a first rotation speed value,a modified geometrical parameter value calculated at a second rotationspeed value, as a function of data of a model representing a trend ofthe elasticity parameter as a function of the speed parameter.

In other words, the processing unit holds in its memory data relating toa trend of the elasticity parameter as a function of the rotation speedof the wheel mounted on the wheel-holder unit 4. Thanks to this data, itis possible to extrapolate the value adopted by the geometricalparameter as a function of the rotation speed of the wheel on thewheel-holder unit 4.

In one example embodiment, the processing unit is programmed to processdata of a first geometrical parameter, calculated at a first rotationspeed, and a second geometrical parameter, calculated at a secondrotation speed, in order to derive a first modelling parameterrepresenting a variation of the geometrical parameter as a function ofthe rotation speed.

More specifically, by taking at least two different rotation speedmeasurements (and using the roller to apply the same predeterminedradial force on the tyre tread), it is possible to define at least twotest points on a graph where a first Cartesian axis (or axis ofabscissas) shows values of the rotation speed of the wheel mounted onthe wheel-holder unit 4 and a second Cartesian axis (axis of ordinates)shows values of the geometrical parameter, that is, in a rotationspeed-geometrical parameter plane. The processing unit is programmed tocalculate a second angular coefficient of a straight line passingthrough the at least two test points in the rotation speed-geometricalparameter plane. Based on a hypothesis of linearity, this angularcoefficient is the first modelling parameter.

In a further example embodiment, the processing unit is configured tocalculate the first modelling parameter from a second plurality of testpoints in the rotation speed-geometrical parameter plane, for example bycalculating the coefficients of a linear regression in the rotationspeed-geometrical parameter plane.

If the hypothesis of linearity is not satisfied, the processing unit isprogrammed to calculate, by means of an iterative algorithm, a secondplurality of parametric coefficients of a second parametric function forinterpolating the second plurality of test points.

Preferably, the machine 1 comprises a pressure sensor for measuring apressure parameter indicating a tyre inflation pressure.

The processing unit is programmed to derive, from a first value of thegeometrical parameter calculated at a first inflation pressure, amodified value of the geometrical parameter at which the geometricalparameter adopts a predetermined or user set value. In other words, theprocessing unit contains data relating to a trend of the geometricalparameter as a function of the pressure parameter and is programmed tosuggest an inflation pressure value at which the geometrical parameteradopts a predetermined or user set value.

In a further example embodiment, the processing unit is programmed toprocess a first value of the geometrical parameter at a first inflationpressure and a second value of the geometrical parameter at a secondinflation pressure in order to derive data representing a trend of thegeometrical parameter as a function of the inflation pressure. Morespecifically, by taking at least two different inflation pressuremeasurements (keeping constant the radial load applied by the roller 2on the tyre and the rotation speed of the wheel mounted on thewheel-holder unit 4), it is possible to define at least two test pointson a graph where a first Cartesian axis (or axis of abscissas) showsvalues of the tyre inflation pressure and a second Cartesian axis (axisof ordinates) shows values of the geometrical parameter, that is, in aninflation pressure-geometrical parameter plane. The processing unit isprogrammed to calculate an angular coefficient of a straight linepassing through the at least two test points in the inflationpressure-geometrical parameter plane. Based on a hypothesis oflinearity, this angular coefficient is a second modelling parameter.

In a further example embodiment, the processing unit is configured tocalculate the second modelling parameter from a third plurality of testpoints in the inflation pressure-geometrical parameter plane, forexample by calculating the coefficients of a linear regression.

If the hypothesis of linearity is not satisfied, the processing unit isprogrammed to calculate, by means of an iterative algorithm, a thirdplurality of parametric coefficients of a third parametric function forinterpolating the third plurality of test points in the inflationpressure-geometrical parameter plane.

In one example embodiment, the processing unit is programmed to derive atrend of the elasticity parameter as a function of the tyre inflationpressure. In other words, the processing unit is programmed to calculatea variation of the angular coefficient in the radial force-geometricalparameter plane as a function of the tyre inflation pressure.

Preferably, the processing unit is programmed to derive a trend of theelasticity parameter as a function of the rotation speed of the wheelmounted on the wheel-holder unit 4 and of the inflation pressure. Inother words, the processing unit is configured to derive a trend of theelasticity parameter as a function of two variables. This trend is, forexample, represented by a surface in a three-dimensional space.

In an example embodiment, the processing unit is configured to processdata relating to at least one control parameter for each wheel of avehicle (that is, for at least four wheels). The processing unit isprogrammed to suggest an ameliorative configuration as a function of thecontrol parameter. This ameliorative configuration refers to one or moreof the following options:

-   -   positioning of the wheels on a vehicle;    -   coupling of a tyre to a wheel rim;    -   relative angular position of a tyre relative to a wheel rim.

According to the disclosure, the control parameter is one of theparameters from the following list:

-   -   geometrical parameter;    -   wheel eccentricity;    -   tyre tread depth;    -   wheel conicity.

Preferably, the control unit is programmed to compare, for each simplecombination of wheels taken two at a time, the control parametersrelating to each wheel and to calculate an analysis parameter.

More specifically, there are six simple combinations of four wheelstaken two at a time. The control unit is configured to calculate sixanalysis parameters. The analysis parameters are calculated by comparingat least two control parameters, each of which relates to one of thefour wheels.

In an example embodiment, a value of an analysis parameter is determinedby an absolute value of a difference between a first control parameterrelating to a first wheel and a second control parameter relating to asecond wheel. The control unit is configured to identify at least onepair of wheels which minimizes a value of the analysis parameter. Inother words, the processing unit is configured to identify a minimumparameter from among the six analysis parameters deriving from thesimple combinations of four wheels taken two at a time.

Preferably, a pair of wheels which minimizes the value of the analysisparameter is coupled together on the same axle of a vehicle. Still morepreferably, a pair of wheels which minimizes the value of the analysisparameter is coupled together on a front axle of a vehicle.

It should be noted that the choice by the tyre service specialist of acertain control parameter (for example, tyre tread depth) might lead toidentification of a pair of wheels different from the pair that would beidentified if another control parameter (for example, the geometricalparameter) were chosen. It should be noted that this disclosure allowsestimating the variation of the control parameters (and in particular,the geometrical parameter) as a function of the tyre inflation pressureto compensate, by acting on the inflation pressure, for the effects ofthe choice of control parameter on the ameliorative configuration.

Also defined according to this description is a method for performingdiagnostic assessment of a vehicle wheel, in a wheel service machine,comprising the following steps:

-   -   rotating the wheel about a first axis A;    -   positioning a roller, whose axis of rotation D is parallel to        the first axis A, in contact with the wheel tyre tread to apply        a predetermined radial force;    -   acquiring at least one force parameter representing a radial        force transmitted to the roller 2 by the tyre;    -   acquiring at least one position parameter representing a        position of the roller relative to the first axis A;    -   processing the position parameter to calculate at least one        value of a geometrical parameter representing a distance between        the first axis A and a surface of the roller in contact with the        tyre tread to derive a pair of values comprising a value of the        radial force measured by the first force sensor 40 when the        roller 2 is in the active position and a corresponding value of        the geometrical parameter calculated.

In one embodiment of this disclosure, the method for performingdiagnostic assessment of a vehicle wheel comprises the following steps:

-   -   repositioning the roller 2 in contact with the wheel tyre tread        to apply a second predetermined radial force;    -   acquiring at least one further force parameter representing a        radial force transmitted to the roller 2 by the tyre;    -   acquiring at least one further position parameter representing a        position of the axis D of the roller 2 relative to the first        axis A;    -   processing the further position parameter to calculate at least        one value of a further geometrical parameter representing a        distance between the first axis A and a surface of the roller in        contact with the wheel tyre tread and deriving a further pair of        values;    -   calculating at least one value of an elasticity parameter,        representing the elasticity of the wheel to radial flattening,        by comparing the pair of values with the further pair of values.

If the processing unit is connected to the drive unit 7 a of thewheel-holder unit 4 to measure a wheel rotation speed parameter, themethod for performing diagnostic assessment of a vehicle wheel comprisesthe following steps:

-   -   acquiring at least one speed parameter representing a first        rotation speed of the wheel mounted on the wheel-holder unit;    -   calculating, from a geometrical parameter value calculated at        the first rotation speed, a modified geometrical parameter value        calculated at a second rotation speed, as a function of data of        a model representing a trend of the geometrical parameter as a        function of the speed parameter.

If the processing unit is connected to a pressure sensor to measure atyre inflation pressure parameter, the method for performing diagnosticassessment of a vehicle wheel comprises the following steps:

-   -   acquiring a tyre inflation pressure parameter representing a        first tyre inflation pressure;    -   calculating, from data representing a trend of the geometrical        parameter as a function of the inflation pressure, a modified        pressure parameter value at which the geometrical parameter        adopts a predetermined or user set value.

It should be noted that this description provides a method for assistingthe tyre service specialist, comprising the following steps:

-   -   preparing four wheels;    -   measuring, for each wheel, a control parameter representing a        property of the wheel.    -   processing the control parameters for each simple combination of        wheels taken two at a time to obtain an analysis parameter for        each simple combination;    -   mounting on an axle of a vehicle a pair of wheels which        minimizes the analysis parameter.

Preferably, the vehicle axle is the front axle of the vehicle.

Preferably, the control parameter represents one of the wheel propertiesfrom the following list:

-   -   geometrical parameter;    -   conicity;    -   eccentricity;    -   tread depth.

The paragraphs listed below, labelled with alphanumeric references, arenon-limiting example modes of describing this invention.

A. A wheel service machine, comprising:

-   -   a wheel-holder unit, rotatable about a first axis;    -   a roller rotatable about a corresponding axis of rotation        parallel to the first axis and movable towards and away from the        first axis between an active position, where it is in contact        with the tyre tread of a wheel mounted on the wheel-holder unit,        to a non-interference position relative to the tyre;    -   at least one force sensor connected to the roller for detecting        a first signal, representing a radial force transmitted to the        roller by the tyre in a direction perpendicular to the axis of        the roller, and/or a second signal, representing a lateral force        transmitted to the roller by the tyre in a direction parallel to        the axis of the roller;    -   a processing unit connected to the first and the second load        cell to receive the corresponding signals detected and process        them,    -   a contactless distance sensor 43 movable along an axis parallel        to the first axis and configured to scan a profile of the wheel        mounted on the wheel-holder unit, wherein the processing unit is        connected to the distance sensor to receive a measurement signal        from it and programmed to compare the measurement signal        detected by the distance sensor with the signal detected by the        at least one force sensor.

A1. The machine according to paragraph A, comprising a first sensorforce, connected to the roller for detecting the first signal, andsecond sensor force, connected to the roller for detecting the secondsignal.

A2. The machine according to paragraph A or A1, wherein the processingunit is programmed to acquire in a synchronized fashion the measuringsignal detected by the sensor distance and the at least one first and asecond signal detected by the at least one sensor force connected to theroller in order to obtain a succession of pairs of values of saidsignals, wherein a first value of the pair belongs to the first orsecond signal and a second value of the pair belongs to the measuringsignal, wherein each pair of values relates to the same angular positionof the wheel-holder unit.

A3. The machine according to paragraph A2, wherein the processing unitis programmed to acquire in a synchronized fashion a measuring signaldetected by the distance sensor positioned in a stationary position andthe signal detected by the at least one force sensor, in order to derivea succession of pairs of values of the signals, wherein each pair ofvalues relates to a same angular position of the wheel-holder unit and asame position of the distance sensor.

A4. The machine according to paragraph A2 or A3, wherein the processingunit is programmed to acquire in a synchronized fashion the measuringsignal detected by the distance sensor during a relative movement alongthe axis parallel to the first axis (A) and the second signal detectedby the at least one force sensor, in order to derive a succession ofpairs of values of the signals, wherein each pair of values relates to asame angular position of the wheel-holder unit.

A5. The machine according to any one of the preceding paragraphs,wherein the processing unit is programmed to develop in Fourier seriesthe at least one first or second signal detected by the at least oneforce sensor and the measurement signal detected by the distance sensor,to calculate one or more diagnostic parameters given by the ratio of thecoefficients of the Fourier developments relating to correspondingharmonics.

A6. The machine according to paragraph A3, wherein the processing unitis programmed to develop in Fourier series the first signal detected bythe at least one force sensor and the measurement signal detected by thedistance sensor synchronized together, to calculate one or morediagnostic parameters given by the ratio of the coefficients of theFourier developments relating to corresponding harmonics.

A7. The machine according to paragraph A4, wherein the processing unitis programmed to develop in Fourier series the second signal detected bythe at least one force sensor and the measurement signal detected by thedistance sensor synchronized together, to calculate one or morediagnostic parameters given by the ratio of the coefficients of theFourier developments relating to corresponding harmonics.

A8. The machine according to any one of the preceding paragraphs,wherein the processing unit is connected to rotational sensor to receivea signal representing the angular position of the wheel-holder unit.

A9. The machine according to any one of the preceding paragraphs,wherein the wheel service machine is a tyre changer machine or abalancing machine.

B. A method for carrying out a diagnostic assessment of a wheel of avehicle, in a wheel service machine, comprising the following steps:

-   -   rotation of the wheel about a first axis;    -   positioning a roller, oriented with its axis of rotation        parallel to the first axis, in contact with a tyre tread of the        wheel;    -   detecting at least a first signal, representing a radial force        transmitted to the roller by the tyre in a direction        perpendicular to the axis of the roller, or a second signal,        representing a lateral force transmitted to the roller by the        tyre in a direction parallel to the axis of the roller;    -   processing of the at least one first or second signal,    -   detecting a measurement signal of a distance sensor, movable        along an axis parallel to the first axis and configured to scan        a profile of the wheel, wherein the processing step comprises a        comparison between the at least one first or second signal and        the measurement signal detected by the distance sensor.

B1. The method according to paragraph B, wherein a third signal isdetected by the distance sensor positioned in a stationary position,during the rotation of the wheel, and acquired simultaneously with thefirst signal detected by the at least one force sensor, wherein thethird and first signal are acquired in a synchronized fashion, to derivea succession of pairs of values of the signals, wherein a first value ofthe pair belongs to the first signal and a second value of the pairbelongs to the third signal, wherein each pair of values relates to asame angular position of the wheel-holder unit.

B2. The method according to paragraph B or B1, wherein a fourth signalis detected by the distance sensor during a movement of the latterparallel to the first axis, during the rotation of the wheel, and isacquired simultaneously with the second signal detected by the at leastone force sensor, wherein the fourth and second signal are acquired inorder to derive a succession of pairs of values of the signals, whereina first value of the pair belongs to the first signal and a second valueof the pair belongs to the third signal, wherein each pair of valuesrelates to a same angular position of the wheel-holder unit.

B3. The method according to any one of paragraphs from B to B2, whereinthe processing comprises a development in Fourier series of the at leastone first or second signal detected by the at least one force sensor andthe measurement signal detected by the distance sensor, to calculate oneor more diagnostic parameters given by the ratio of the coefficients ofthe Fourier developments relating to corresponding harmonics.

B4. The method according to paragraph B3, wherein the processingcomprises a development in Fourier series of the first and third signalsand a calculation of one or more diagnostic parameters given by theratio of the coefficients of the Fourier developments relating tocorresponding harmonics.

B5. The method according to paragraph B2, wherein the processingcomprises a development in Fourier series of the second and fourthsignals and a calculation of one or more diagnostic parameters given bythe ratio of the coefficients of the Fourier developments relating tocorresponding harmonics.

C. A wheel service machine 1 comprising:

-   -   a frame;    -   a wheel-holder unit 4 rotating about a first axis A;    -   a roller 2 rotating about an axis parallel to the first axis and        movable towards and away from the wheel-holder unit 4 along an        operating trajectory such that the axis of the roller 2 remains        parallel to the first axis, between a position of        non-interference with the tyre of a wheel mounted on the        wheel-holder unit 4 and an active position where it applies a        predetermined force to the tyre tread;    -   a connecting structure to movably connect the roller 2 to the        frame.    -   at least one force sensor 40 connected to the roller 2 for        measuring values of a force parameter representing a radial        force transmitted to the roller 2 by the tyre;    -   at least one position sensor configured to measure values of a        position parameter representing a position of the roller 2        relative to the frame;    -   a processing unit connected to the at least one force sensor 40        and to the at least one position sensor,

wherein the processing unit is configured to calculate, as a function ofthe position parameter, a geometrical parameter representing a distancebetween the first axis and a surface of the roller 2 in contact with thetyre tread when the roller 2, is in the active position, and to derive apair of values comprising a value of the radial force measured by theforce sensor 40 when the roller 2 is in the active position and acorresponding value of the geometrical parameter calculated.

C1. The machine according to paragraph C, wherein the position sensor iscoupled to the connecting structure at a predetermined position todetect a position of a predetermined zone of the connecting structureand wherein the processing unit holds in its memory informationrepresenting a relative position between the predetermined zone and theaxis of the roller 2.

C2. The machine according to paragraph C1, wherein the connectingstructure comprises an articulated arm 38 connected to the roller 2 inorder to move the roller 2 by rotation about a respective axis, spacedfrom the axis of the roller 2, and wherein the position sensor isconfigured to derive a rotation of the articulated arm 38 relative tothe frame.

C3. The machine according to any one of the preceding paragraphs,wherein the processing unit is programmed to acquire, in addition to thepair of values derived in relation to the predetermined force applied bythe roller 2 to the tyre tread, at least one further pair of valuescomprising a further radial force value and a corresponding furthervalue of the geometrical parameter, and is programmed to calculate atleast one value of an elasticity parameter representing an elasticity ofthe wheel to radial flattening, by comparing said pair of values withsaid further pair of values.

C4. The machine according to paragraph C3, wherein the processing unitis connected to a drive unit 7 a of the wheel-holder unit 4 to measure awheel rotation speed parameter and is programmed to derive, from ageometrical parameter value calculated at a first rotation speed, amodified geometrical parameter value calculated at a second rotationspeed, as a function of data of a model representing a trend of theelasticity parameter as a function of the speed parameter.

C5. The machine according to paragraph C3 or C4, wherein the processingunit is programmed to process a first value of the geometricalparameter, corresponding to a first rotation speed, and a second valueof the geometrical parameter, corresponding to a second rotation speed,in order to derive at least one value of a first modelling parameterrepresenting a variation of the geometrical parameter as a function ofthe rotation speed.

C6. The machine according to any one of the preceding paragraphs,wherein the processing unit is connected to a pressure sensor to measurea tyre inflation pressure parameter and is programmed to derive, from afirst value of the geometrical parameter calculated at a first inflationpressure, a modified value of the pressure parameter at which thegeometrical parameter adopts a predetermined or user set value.

C7. The machine according to any one of the preceding paragraphs,wherein the processing unit is connected to a pressure sensor to measurea tyre inflation pressure parameter and wherein the processing unit isprogrammed to process a first value of the geometrical parameter at afirst inflation pressure and a second value of the geometrical parameterat a second inflation pressure in order to derive data representing atrend of the geometrical parameter as a function of the inflationpressure.

C8. The machine according to any one of the preceding paragraphs,wherein the processing unit is connected to an angular position sensorto receive a signal representing an angular position of a wheel mountedon the wheel-holder unit 4, and wherein the processing unit isprogrammed to acquire a plurality of values of the radial forceparameter as a function of an angular position of the wheel about thefirst axis, in order to calculate a radial force value averaged relativeto a predetermined angle of rotation imparted to the wheel about thefirst axis.

C9. The machine according to any one of the preceding paragraphs,wherein the processing unit is configured to receive a signalrepresenting radial force during a rotation of the wheel, has access toa value of an elasticity parameter representing an elasticity of thewheel to radial flattening, and is configured to derive an eccentricityparameter as a function of that signal and that elasticity parameter.

C10. The machine according to any one of the preceding paragraphs,wherein the processing unit is configured to process data relating to atleast one control parameter for four wheels of a vehicle and isprogrammed to suggest an ameliorative configuration as a function ofthat control parameter, wherein the ameliorative configuration refers toone or more of the following options:

-   -   positioning of the wheels on a vehicle;    -   coupling of a tyre to a wheel rim;    -   relative angular position of a tyre relative to a wheel rim,

and wherein the control parameter is one of the parameters from thefollowing list:

-   -   geometrical parameter;    -   wheel eccentricity;    -   tyre tread depth;    -   wheel conicity.

C11. The machine according to paragraph C10, wherein the processing unitis programmed to compare, for each simple combination of wheels takentwo at a time, the control parameters relating to each wheel and toobtain an analysis parameter, in order to identify at least one pair ofwheels which minimizes the analysis parameter.

C12. The machine according to any one of the preceding paragraphs,wherein the wheel service machine 1 is a tyre changer machine.

D. A method for performing diagnostic assessment of a vehicle wheel, ina wheel service machine, comprising the following steps:

-   -   rotating the wheel about a first axis;    -   positioning a roller, whose axis of rotation is parallel to the        first axis, in contact with the wheel tyre tread to apply a        predetermined radial force;    -   acquiring at least one force parameter representing a radial        force transmitted to the roller 2 by the tyre;    -   acquiring at least one position parameter representing a        position of the roller relative to the first axis;    -   processing the position parameter to calculate at least one        value of a geometrical parameter representing a distance between        the first axis and a surface of the roller in contact with the        tyre tread and to derive a pair of values comprising a value of        the radial force measured by the force sensor when the roller is        in the active position and a corresponding value of the        geometrical parameter calculated.

D1. The method according to paragraph D, further comprising thefollowing steps:

-   -   repositioning the roller in contact with the wheel tyre tread to        apply a second predetermined radial force;    -   acquiring at least one further force parameter representing a        radial force transmitted to the roller 2 by the tyre;    -   acquiring at least one further position parameter representing a        position of the axis of the roller relative to the first axis;    -   processing the further position parameter to calculate at least        one value of a further geometrical parameter representing a        distance between the first axis and a surface of the roller in        contact with the wheel tyre tread and to derive a further pair        of values;    -   calculating at least one value of an elasticity parameter,        representing the elasticity of the wheel to radial flattening,        by comparing the pair of values with the further pair of values.

D2. The method according to paragraph D or D1, further comprising thefollowing steps:

-   -   acquiring at least one speed parameter representing a first        rotation speed of the wheel mounted on the wheel-holder unit;    -   calculating, from a geometrical parameter value calculated at        the first rotation speed, a modified geometrical parameter value        calculated at a second rotation speed, as a function of data of        a model representing a trend of the geometrical parameter as a        function of the speed parameter.

D3. The method according to any one of paragraphs from D to D2 furthercomprising the following steps:

-   -   acquiring a tyre inflation pressure parameter representing a        first tyre inflation pressure;    -   calculating a modified pressure parameter value at which the        geometrical parameter adopts a predetermined or user set value,        as a function of data of a model representing a trend of the        geometrical parameter as a function of the pressure parameter.

D4. The method according to any one of paragraphs from D to D3, furthercomprising the following steps:

-   -   preparing four wheels;    -   measuring, for each wheel, a control parameter representing a        property of the wheel.    -   processing the control parameters for each simple combination of        wheels taken two at a time to obtain an analysis parameter for        each simple combination;    -   mounting on an axle of a vehicle a pair of wheels which        minimizes the analysis parameter.

D5. The method according to paragraph D4, wherein the control parameterrepresents one of the wheel properties from the following list:

-   -   conicity;    -   eccentricity;    -   tread depth;    -   geometrical parameter.

The invention claimed is:
 1. A device for locking a rim of a wheel to awheel-holder unit equipped with a supporting plate and a hollow rotaryshaft having an end portion which projects in a cantilever fashion fromthe supporting plate, the device comprising: a centring cone having athrough hole; a clamping rod having at a first end a locking elementwhich can be inserted inside the hollow shaft to prevent a movement ofthe clamping rod along a first axis of the wheel-holder unit, and havinga threaded portion at a second end; a clamping element coupled to thethreaded portion and which can be rotated so as to move along an axis ofthe clamping rod, a centring flange, wherein the centring flange isoperatively interposed between the centring cone and the clampingelement and has a central through hole, a first face and a second facefrom, which two or more centring rods project in a cantilever fashionwhich can be inserted into corresponding radial openings of the rim,wherein the first end of the clamping rod is operatively inserted in thehole of the centring flange and in the hole of the centring cone, withthe same direction as that in which the centring rods project, oppositeto the direction that along which the centring cone is tapered.
 2. Thedevice according to claim 1, wherein the hole of the centring cone canbe inserted in the end portion of the hollow shaft.
 3. The deviceaccording to claim 1, wherein the centring cone is tapered from a firstenlarged end to a second narrow end and comprises an annular protrusionwhich is smaller in diameter to the first enlarged end and projectingfrom the first end away from the second end.
 4. The device according toclaim 1, wherein at least one of the centring rods of the centringflange forms a recess on a corresponding end surface, to receive ananti-rotation pin connected to the supporting plate and orientedparallel to an axis of the hole of the centring flange.
 5. The deviceaccording to claim 1, wherein the two or more centring rods can movetowards and away from the hole of the centring flange.
 6. The deviceaccording to claim 5, wherein the two or more centring rods arepositioned along a circumference equispaced from each other around thecentral hole of the centring flange and are interconnected with eachother by means of a kinematic mechanism using a gear assembly.
 7. Thedevice according to claim 1, wherein at least one coupling element,designed to be coupled to the supporting plate, protrudes from the firstface of the centring flange.
 8. A wheel service machine, comprising: awheel-holder unit equipped with a supporting plate and a hollow rotaryshaft having an end portion which projects in a cantilever fashion fromthe supporting plate; a locking device for fixing a rim of a wheel tothe wheel-holder unit, wherein the locking device is a device accordingto claim
 1. 9. The machine according to claim 8, wherein the supportingplate of the wheel-holder unit comprises: movable annular elementdefining a supporting surface for receiving and supporting the centringcone; an elastic element interposed between the annular element and thehollow shaft, to allow the movable annular element to move along adirection parallel to the first axis of the wheel-holder unit.
 10. Themachine according to claim 9, wherein the movable annular element of thesupporting plate of the wheel-holder unit has at least one toothslidably coupled to a groove defined by the hollow shaft and orientedparallel to the first axis of the wheel-holder unit.
 11. The machineaccording to claim 8, comprising an anti-rotation system so as toprevent a relative rotation between the rim mounted on the wheel-holderunit and the supporting plate, wherein the anti-rotation systemcomprises an anti-rotation pin oriented parallel to the first axis ofthe wheel-holder unit and projecting in the same direction as the endportion of the hollow shaft and connected to an end of a shaped armrotating about an axis parallel to the first axis of the wheel-holderunit, for varying a distance of the anti-rotation pin relative to thefirst axis of the wheel-holder unit, wherein the anti-rotation pin isconnectable to an end of at least one of the centring rods of thecentring flange.
 12. A method for locking a rim of a wheel to awheel-holder unit equipped with a supporting plate and a hollow rotaryshaft having an end portion which projects in a cantilever fashion fromthe supporting plate wherein the method comprises the following steps:preparing a centring cone having a through hole; coupling the centringcone to the end portion of the rotary shaft, in such a way that thecentring cone is tapered in the same direction to that in which therethe end portion of the hollow shaft extends; positioning the rim on thesupporting plate in such a way that a central hole of the rim is coupledto the centring cone; preparing a centring flange having a first faceand a second face from which two or more centring rods project in acantilever fashion; inserting centring rods of the centring flange inradial openings of the rim until the second face of the centring flangeis in contact with the rim; preparing a clamping rod having, at a firstend, a locking element and, at a second threaded end, a clamping elementcoupled thereto; inserting the locking element of the clamping rodinside the hollow shaft to prevent a movement of the clamping rod alonga first axis of the wheel-holder unit; rotating the clamping element tomove it along the clamping rod, until it presses on the first face ofthe centring flange to clamp against the rim.
 13. The method accordingto claim 12, wherein the centring cone is positioned in contact with amovable annular element of the supporting plate, supported elasticallyto be able to undergo movements along a direction parallel to the firstaxis of the wheel-holder unit.
 14. The method according to claim 12,wherein the wheel-holder unit comprises an anti-rotation system so as toprevent a relative rotation between the rim mounted on the wheel-holderunit and the supporting plate, equipped with an anti-rotation pinoriented parallel to the first axis of the wheel-holder unit andprojecting in the same direction as the end portion of the hollow shaft,and wherein the anti-rotation pin is coupled to an end of one of thecentring rods of the centring flange.